DE4428839C2 - Alkali-zinc-silicate glass-ceramics and glasses and process for producing the glass-ceramics - Google Patents

Abstract

Alkali-zinc-silicate glass-ceramic or glass comprises (by wt.) SiO2 (52-63.5%), Me(III)2O3 (8.5-13%), K2O (0-20.5%), Na2O (1.5-20%), Li2O (0-5%), ZnO (2-8, especially 3.1-8, %), Me(II)O (2.5-6.5%), TiO2 + ZrO2 (0.5-6%), SnO2 (0-9.5%), P2O5 (0-4%), F (0-2%) and CeO2 (0-3%). Me(III)2O3 comprises Al2O3 (0-13%) and La2O3 (0-9.5%). Me(III)O comprises CaO (0-3.5%), BaO (0-4.5%) and MgO (0-5%). An Independent claim is given for production of the glass-ceramic by heating a glass made up of the above components at 600-900 degrees C for 0.5-5 hours.

Description

The invention relates to alkali-zinc-silicate glass ceramics and glasses, and in particular to those which, owing to their advantageous properties, such as linear thermal expansion coefficients which can be set in the range from 8.0 to 18.7 × 10 ^-6 K ^-1 , and low processing temperatures are suitable as dental material.

Metallic dental restorations are used in dentistry usually veneered with ceramic layers to achieve this Restoration looks like that of natural teeth align. Such blinded restorations are also referred to as veneering ceramics or metal ceramics. Um now Tensions between the metal structure and the ceramic layer avoid, it is necessary that the coefficient of thermal expansion The ceramic materials are adapted to those of the metal are.

It is known that leucite-containing glass ceramics are very high have linear thermal expansion coefficients. This  are due to the content of leucite, which is caused by controlled crystallization from a corresponding output glass is formed.

So that a dental glass ceramic for veneering the entire Range of dental metals and alloys used, such as e.g. B. Titanium up to alloys with a high gold content can be set, it is necessary that its expansion coefficient is adjustable in a wide range. Provided the dental glass ceramic also as a correction material for Firing ceramics are to be used, so are further especially low sintering temperatures of less than 880 ° C and suitable optical properties, such as high translucency, very desirable.

Known glass ceramics and glasses meet the requirement Thermal expansion adjustable in a wide range coefficient and a low processing temperature often not. In addition, the known dental materials in many cases physiologically not entirely harmless Components such as B. Sb₂O₃, or it is mandatory Lich to add B₂O₃ to them for dental materials to achieve desired properties. According to investigations by the Lead inventors on basic glasses of the system SiO₂-Al₂O₃-Na₂O-K₂O low B₂O₃ additions of about 3 wt .-% to an unacceptable Deterioration of chemical resistance and high B₂O₃- Contents of approx. 12% by weight at too low an expansion coefficients.

Dental ceramic materials containing B₂O₃ are z. B. from DE-OS 39 11 460 and DE-PS 41 38 875 known. These materials have relatively low processing temperatures and can be used to veneer dental alloys. However, their coefficient of thermal expansion can only be set in the range of approximately 13 to 14 × 10 ^-6 K ^-1 .

The materials also contain Sb₂O₃, but none ZnO and no ZrO₂.

A ceramic material for veneering metallic dentures is also known from DE-OS 40 31 168. Even if the coefficient of expansion of this material should be adjustable in a range from 8 to 17.5 × 10 ^-6 K ^-1 , the material still contains 0.7 to 2.5% by weight of B₂O₃. Furthermore, there is no ZnO and no ZrO₂ in the material.

Porcelain masses with a high content of B₂O₃ from 7 to 33% by weight and processing temperatures in the range of 800 ° C are known from US Pat. No. 5,176,747. These masses can be used as Dental porcelain for veneering titanium or titanium alloy gene can be used. The B₂O₃ used serves both to reduce the processing temperature as well as Reduction of the coefficient of thermal expansion. About that In addition, the B₂O₃ also has an influence on the bond strength between the metal substrate and the ceramic. Similar ceramic materials with a content of 8 to 17% by weight B₂O₃ are described in EP-A-468 435. These materials do not contain ZnO and can also be used for veneering Dental restorations, such as crowns, bridges or prosthesis parts are used, which are made of titanium or titanium alloys are manufactured.

Furthermore, EP-A-0 155 564 contains leucite-containing glass ceramics known, but the B₂O₃ and physiologically harmless Sb₂O₃ included.

The invention is based on the object of providing glass ceramics and glasses which can be processed at low temperatures by sintering, which have a linear thermal expansion coefficient which can be set in the range from in particular 8.0 to 18.7 × 10 ^-6 K ^-1 and at the same time advantageous optical properties, such as high translucency and opalence, as well as excellent chemical resistance and can be produced without the addition of B₂O₃ and / or physiologically not completely harmless components and are therefore advantageously suitable for use in dental technology.

This task is accomplished through the alkali zinc silicate glass ceramic according to claims 1 to 6 and the alkali zinc silicate glass solved according to claim 9.

The present invention also relates to Process for the production of glass ceramics.

The alkali zinc silicate glass ceramic according to the invention and also the alkali zinc silicate glass according to the invention are thereby marked that they contain the following components:

in which

• a) the specified amount of Me (III) ₂O₃ from 0 to 13 wt .-% Al₂O₃ and 0 to 9.5% by weight of La₂O₃; and
• b) the stated amount of Me (II) O from 0 to 3.5% by weight of CaO, O to 4.5 wt% BaO and 0 to 5.0 wt% MgO

is formed.

Both the glass ceramic and the glass exist essentially from the aforementioned components.

For some of the components of glass ceramics and glass preferred quantity ranges exist. These can be independent can be chosen from each other and are as follows:

It is very particularly preferred that the invention Glass ceramic and the glass according to the invention essentially free of B₂O₃, antimony and / or lead compounds.  

For the production of the glass according to the invention is preferred proceeded so that suitable starting materials such. B. Carbonates, oxides and fluorides, at a temperature in the range from 1350 to 1650 ° C, preferably 1400 to 1600 ° C, over a Period of 30 minutes to 4 hours, preferably one hour up to 2.5 hours, forming a homogeneous melt be melted. The melted glass is then in Water quenched d. H. fritted, and the glass obtained Granules are ground up after drying.

To produce the glass ceramic according to the invention, ins special proceeded so that the granules obtained glass according to the invention of a thermal treatment in a Temperature in the range of 600 to 900 ° C for a period of 30 minutes to 5 hours, preferably 30 minutes to 2 hours which is subjected. This is preferably used Glass before heat treatment to a powder with a Grain size of less than 90 µm ground and sieved. The thermal treatment can also be carried out as part of the Manufacture of molded dental products from the Invention according to glass required heat treatments, such as sintering processes.

Using scanning electron microscopic examinations found that the glasses of the invention free of Crystals are or have only very few crystals. In contrast, the glass ceramics according to the invention contain Crystals, especially leucite crystals, which are characterized by the controlled surface crystallization in the context of thermal Treatment were formed. The leucite preferably form the main crystal phase in glass ceramics, and the average size of the leucite crystals is preferably less than 5 µm based on the number of crystals.

In addition to leucite crystals, depending on the chemical Composition of the glass used further crystal phases  be formed. In addition to the different crystal phases you can also micro-heterogeneous segregation areas, d. H. various Glass phases. These areas are in the Rasterelek Tron microscope as small micro-heterogeneous droplet glass phases recognizable with a size of approx. 40 to 250 nm. The existence this drop glass phase or of crystals affects the optical properties, such as B. opalescence and translucency, the glass ceramics and glasses according to the invention.

The linear thermal expansion coefficient of the glass ceramics and glasses according to the invention can preferably be set in the range from 8.0 to 18.7 × 10 ^-6 K ^-1 , measured in the temperature range from 100 to 400 ° C. It is surprising that despite the high content of 52.5 to 63.5 wt .-% SiO₂ and without the addition of B₂O₃ the glass ceramics and glasses according to the invention can be given both high and low expansion coefficients. According to the prior art, however, the addition of B₂O₃ is mandatory in most cases for setting low expansion coefficients.

Through the use of monovalent network conversion ions, such as Potassium, sodium and lithium, and by using fluorine could the processing temperature can be reduced. So they can Glasses and glass ceramics according to the invention in powder form Temperatures of preferably 640 to 850 ° C sintered together and processed with it.

The high content of ZnO in the glass ceramics according to the invention and glasses contribute significantly to the good chemical resistance at and reduces their viscosity compared to ZrO₂. In addition, ZnO is characterized by an excellent physiological tolerance.

In addition to the components mentioned above, the fiction modern glass ceramics and glasses also additives, such as e.g. B. dyes, in particular color pigments, oxides of 3d  Elements or metal colloids, or fluorescent substances, ins special ytterbium silicate doped with d and f elements, contain. Other suitable additives for changing e.g. B. the optical and / or thermal properties of glass ceramics and glasses according to the invention are further glasses, Ceramics, other glass ceramics, opacifiers and / or Stabilizers.

The glass ceramics and glasses according to the invention can either solely as a dental material or as part of Dentalmate rialien, such as. B. dental ceramic powders can be used. For this purpose, the glass according to the invention and the invention appropriate glass ceramic, preferably in the form of a powder with a particle size of in particular less than 90 microns used. This glass ceramic or glass powder is suitable in a particularly advantageous manner as correction material for metal-ceramic or all-ceramic dental superstructures, such as B. a partial crown, a crown or a bridge. For For this purpose, the powder is placed on the desired places Dental superstructure applied and at temperatures of 640 up to 850 ° C sintered together in a vacuum furnace. Here can the properties of the powder such. B. thermal Expansion coefficient and optical properties to that of sintered base material can be adapted.

In a further preferred embodiment of the invention, the glass ceramic according to the invention can also be used as a layer or veneering material for all-ceramic, metallic or dental superstructures in the form of alloys. For this purpose, the powdered glass ceramic is mixed with water and applied to the metallic or all-ceramic substrate. After forming the desired dental restoration, such as. B. bridge or crown, this is densely sintered at temperatures of 640 to 850 ° C to the finished, molded dental product. It is particularly advantageous that the coefficient of thermal expansion of the glass ceramic can be varied within a wide range, namely to 8.0 × 10 ^-6 K ^-1 for a titanium substrate and approximately 16.0 × 10 ^-6 K ^-1 for a substrate made of gold or alloy with high gold content adjusted and can thus be adapted to the expansion coefficient of the substrate used.

It is particularly surprising that the inventive Glass ceramics and glasses a combination of low ver working temperature, adjustable in a wide range thermal expansion coefficient and very good chemical Have durability.

Shaped dental products according to the invention that have a content on the glass ceramic according to the invention or the inventive Have glass, especially dental restorations, such as e.g. B. crowns, partial crowns and bridges, in question.

The invention is illustrated below with the aid of examples explained.

Examples Examples 1 to 18

There were a total of 18 different glass casings according to the invention miken and 18 different glasses according to the invention. They had the chemical shown in Table I. Compositions.

For some of the glass ceramics and glasses are in Table II selected properties specified on test specimens the respective glass or glass ceramic have been. Further can be found in Table II under "Tempera turbehandlung "Information on the output used in each case material for the test specimens as well as information on any Heat treatment of the raw material. At all starting materials for which no heat treatment is specified, it was glasses according to the invention. The exit materials with specified heat treatment were inventive appropriate glass ceramics. However, it should be noted that in the case of the No. 10 heat-treated glass a corresponding glass ceramic occurred when this in Table II specified temperature range for test specimens was sintered.

Table II further shows that a glass ceramic is usually a higher coefficient of expansion than a glass ent speaking chemical composition.

The examples illustrate how by changing the chemi composition and by any heat treatment Glass ceramics and glasses with different properties can be obtained.

Example 19

This example describes the manufacture of a fiction contemporary glass ceramic, which is used as a deep-melting veneer ceramic or as correction material from both veneering and Full ceramics can be used.

First, a starting glass with the in Table I for Example 10 chemical composition prepared. For this purpose, a mixture of oxides, carbonates and fluorides in a platinum / rhodium crucible at a temperature of 1550 to 1600 ° C during a homogenization time of approximately Melted for 2 hours. The glass melt was in water quenched, and the glass frit formed was dried and ground to a grain size of less than 90 µm. On finally the glass powder obtained was added for one hour 750 ° C heat treated, ground again and on a particle sieved to a size of less than 90 µm. With the received Glass ceramic powders were produced and the test specimens in Table II under No. 10 with heat treatment Properties determined.

To measure the coefficient of linear thermal expansion, a rod-shaped green body was produced from the glass ceramic powder, which was fired in a vacuum furnace with a heating rate of 60 ° C / min and a holding time of 1 minute at a temperature of 720 ° C. Glaze firing was then carried out without vacuum at a final temperature of 740 ° C. and a holding time of 1 minute. The linear thermal expansion coefficient for the test specimen obtained was 16.2 × 10 ^-6 K ^-1 , measured in the temperature range from 100 to 400 ° C. The coefficient of expansion of this glass ceramic is thus matched to that of alloys with a high gold content.

Also in the production of platelets instead of rods could the glass ceramic at a very low temperature of only 740 ° C are sintered together. The manufacture of the Platelet was made in such a way that from the glass ceramic powder a green compact in platelet form and this on one with Quartz powder coated firing trays in a vacuum oven at 740 ° C and burned for a minute. The The heating rate of the vacuum furnace was 60 ° C / min.

The determination of the chemical resistance of glass ceramics by treating sintered platelets with 4% vinegar acid in a Soxhlet apparatus according to ISO 6872 led to a very low loss of mass of the glass ceramic of only 0.02%.

By the one adapted to alloys with high gold content linear thermal expansion coefficient, the very good chemical resistance and the low processing temperature is this glass ceramic particularly for sintering onto such Alloys and as correction material for veneering and Suitable for full ceramics.

To achieve linear thermal expansion coefficients which are based on all current gold-containing dental alloys conditions are adapted, the glass ceramic preferably with other powdered glass ceramics and glasses according to the invention a chemical composition given in Table I. be mixed.

Example 20

This example describes the manufacture of a fiction contemporary glass ceramic, which is used as a correction material for full ceramics and used in particular for metal ceramics can be.  

First, a glass with the one in Table I for Example 11 specified composition corresponding to that in Example 19 described procedure melted and ground. The Powder obtained was referred to as Powder I.

Furthermore, a glass was used with that in Table I for Example 12 specified composition also according to the Procedure melted and fried according to Example 19. The dried frit was then at 750 ° C for one hour heat-treated and finally ground in an agate mill and sieved to a particle size of less than 90 µm. The Powder obtained was referred to as Powder II.

By a suitable mixing of these two powders with the glass ceramic powder according to Example 19, the expansion coefficient could be set in the desired manner and the mixture obtained could thus be used as a correction material for sintering onto metal ceramic crowns with very good optical properties. For example, a suitable mixture consisted of 70% by weight of Powder I, 15% by weight of Powder II and 15% by weight of powder according to Example 19, and this mixture had an expansion coefficient of 12.7 × 10 ^-6 K ^-1 .

This mixture was used for correction purposes the point of a metal ceramic crown to be corrected brought, and the crown was at a temperature of 640 ° C fired, working from 580 ° C under vacuum, the Heating rate 60 ° C / min and the holding time was one minute. The finished crown had a very in the corrected place translucent and especially light in the cutting area opalescent appearance and therefore lively.

At a temperature of 730 ° C and a holding time of one Minute were able to place platelets on quartz powder from this mixture be burned. Also showed manufactured according to ISO 6872  and tested platelets from this mixture a very good one Acid resistance of only 0.02% mass loss.

Example 21

This example describes a glass ceramic according to the invention, which as correction material for veneering ceramics and ins can be used especially for all-ceramic crowns.

First, a glass with the one in Table 1 for Example 13 specified chemical composition according to the example 19 described procedure melted and ground. The Glass powder obtained was then at 750 ° C for 30 minutes heat treated. The properties of the glass ceramic obtained are specified in Table II under No. 13.

By appropriately mixing a powder of this glass ceramic with the powder I according to Example 20, the coefficient of expansion could be adjusted so that the mixture obtained could be used as a correction material for sintering onto all-ceramic crowns. A mixture suitable for this purpose contained 80% by weight of the glass ceramic powder and 20% by weight of glass powder I according to Example 20 and had an expansion coefficient of 16.7 × 10 ^-6 K ^-1 , measured in the range from 100 to 400 ° C.

Example 22

This example describes a glass according to the invention which has a linear thermal expansion coefficient of approximately 8.0 × 10 ^-6 K ^-1 , measured in the range from 100 to 500 ° C., and can accordingly be used as a veneering material or correction material for titanium alloys. The glass has a processing temperature, ie a sintering temperature, of less than 880 ° C.

A glass with the chemical composition given in Table I for Example 16 was melted and ground according to the procedure given in Example 19 for its production. Test specimens were produced in accordance with Example 19, but the firing temperature for producing the rod-shaped test specimens for measuring the coefficient of expansion in the first firing was 850 ° C. and the glaze firing was carried out at 830 ° C. A thermal expansion coefficient of 8.1 × 10 ^-6 K ^-1 , measured in the temperature range from 100 to 500 ° C, was determined for the rod-shaped test specimens produced in this way.

The firing temperature of platelets on quartz powder was only 850 ° C, and manufactured according to ISO 6872 and below searched plates from the glass showed a very good acid level Consistency of just 0.01% mass loss. Also owned plates burned from the glass have a very high translucency.

Claims (10)

1. alkali zinc silicate glass ceramic, characterized in that it contains the following components: in which

• a) the specified amount of Me (III) ₂O₃ from 0 to 13 wt .-% Al₂O₃ and 0 to 9.5 wt .-% La₂O₃; and
• b) the stated amount of Me (II) O from 0 to 3.5% by weight of CaO, 0 to 4.5% by weight of BaO and 0 to 5.0% by weight of MgO

is formed. 2. Glass ceramic according to claim 1, characterized in that the amounts of some components are independent of one another as follows: 3. Glass ceramic according to claim 1 or 2, characterized records that it is free of B₂O₃. 4. Glass ceramic according to one of claims 1 to 3, characterized characterized in that it has leucite crystals. 5. Glass ceramic according to claim 4, characterized in that the leucite crystals have an average size of less than 5 µm, based on the number of crystals. 6. Glass ceramic according to one of claims 1 to 5, characterized in that it has a linear thermal expansion coefficient from 8.0 to 18.7 × 10 ^-6 K ^-1 , measured in the range from 100 to 400 ° C. 7. Process for producing the glass ceramic according to a of claims 1 to 6, characterized in that a Glass is made, which the components according to Claim 1 contains, and then the glass produced ßend a heat treatment at 600 to 900 ° C over a Period of 30 minutes to 5 hours is subjected. 8. The method according to claim 7, characterized in that the manufactured glass into one before the heat treatment Powder with a grain size of less than 90 µm is ground and sieved. 9. alkali zinc silicate glass, characterized in that it contains the components according to claim 1.